This invention relates generally to medical devices and more particularly to flexible, power-driven catheters for intravascular surgery and other surgical and in-body medical procedures.
Various types of catheter instruments have been suggested or disclosed for effecting non-invasive or minimally invasive surgical or medical procedures within the body of a person or animal. For example, in U.S. Pat. No. 4,445,509 (Auth) there is disclosed a recanalization catheter designed specifically for cutting away hard, abnormal deposits, such as atherosclerotic plaque, from the inside of an artery, and while supposedly preserving the soft arterial tissue. That recanalization catheter includes a sharp edged, multi-fluted, rotating cutting tip mounted at the distal end of the catheter and arranged to be rotated by a flexible drive shaft extending down the center of the catheter. The rotation of the cutting head is stated as producing a "differential cutting" effect, whereupon relatively hard deposits are cut away from relatively soft tissue. Suction ports are provided in the cutting tip to pull the hard particles produced by the cutting action into the catheter for removal at the proximal end thereof so that such particles do not flow distally of the catheter where they could have an adverse effect on the patient's body.
It has been determined that the use of sharp rotary cutting blades in a revascularization catheter can have various adverse effects on arterial tissue, e.g., snagging, cutting or otherwise damaging the tissue of the artery wall.
In our copending U.S. patent application Ser. No. 914,954, filed on Oct. 3, 1986, entitled Catheter Based Surgical Methods and Apparatus Therefor, assigned to the same assignee as this invention, and whose disclosure is incorporated by reference herein, there is disclosed and claimed catheters and methods of use for effecting a surgical procedure, such as opening an atherosclerotic restriction in an artery, or opening a fallopian tube, destroying or pulverizing a stone in a bodily lumen, etc., at a remote location within the body. The catheters of that invention consist of elongated flexible members of sufficient flexibility and small diameter to enable them to be readily passed through the body of the patient, e.g., through a portion of the vascular system, to the situs of the procedure to be accomplished, e.g., the location of the atherosclerotic plaque in the artery. Those catheters include at their distal end a working head arranged for high speed movement, e.g., rotation, to effect the procedure and without posing any danger to contiguous bodily tissue. In some embodiments, the catheter may eject fluid at the working head to expedite the procedure.
In another of our copending U.S. patent applications, that is, U.S. application Ser. No. 921,973, filed on Oct. 22, 1986, entitled Catheter With High Speed Moving Working Head, assigned to the same assignee as the subject invention, and whose disclosure is incorporated by reference herein, there is disclosed and claimed catheters, their working heads and methods of use for effecting surgical procedures at a remote location within the lumen of the body. Those catheters include rotary working heads having non-sharp impacting surfaces to effect material removal without cutting. The catheters are arranged to eject fluid adjacent the working head to expedite the procedure. When such catheters are used for treating atherosclerotic disease by recanalizing arteries, the catheter is guided through the vascular system of the patient to the site of the vascular occlusion or blockage that has been determined to exist so that the rotary working head is located immediately adjacent the restriction. The working head is then rotated about the longitudinal axis of the catheter at a high rate of speed, e.g., from 10,000 rpm to 200,000 rpm. At the same time, fluid is passed through the catheter and out of its distal end adjacent the working head. The opening of the restriction to allow freer flow of blood is effected by the dilation and/or selective emulsification properties of the catheter's working head. In this connection, during the rotation of the working head fluid jets exiting the distal end of the catheter at the working head are immediately accelerated laterally by portions of the working head so that they are broken up into small segments that develop considerable momentum as they are flung out in all directions, including radial directions, toward the wall of the artery. These liquid segments transfer their momentum to the artery wall, forcing the artery wall outward laterally in all directions, thereby aiding in dilating it.
The rotating working head, with its non-sharp impacting surfaces also serves to differentiate atherosclerotic tissue from normal tissue through the inherent differences in the tissues' physical properties and organizational patterns. Therefore, when the catheter is passed translumenally through a diseased artery, its working head serves to emulsify occlusive lesions not covered with fibrous plaque by repeatedly impacting the material forming the restriction as the working head is rotated, and with minimal risk of puncture or perforation of the contiguous arterial wall. The emulsification process is accomplished by the repeated impaction of the non-sharp impacting surfaces on the materials forming the restriction. This action causes the material to be broken away in small particles. The rotation of the working head also produces a powerful vortex flow at the working head so that any particles produced by the impacting action are drawn back into contact with the impacting surfaces of the rotating working head. Accordingly, those particles are repeatedly impacted over and over, with each impaction reducing the size of the particles further until the resulting particle size is sufficiently small that they can be permitted to flow to downstream tissue without causing any significant deleterious effects to the patient.
For some surgical or other in-body medical applications reciprocatory action of a working head, in conjunction with either rotary motion thereof or alone, may prove beneficial or more effective than pure rotary motion.